MitoNEET (mitochondrial protein containing Asn-Glu-Glu-Thr [NEET] sequence), also known as Cisd1, is an iron-containing protein located on the outer mitochondrial membrane. Based on its original recognition as a binding target of the antidiabetic drug pioglitazone, MitoNEET was considered to be a potential therapeutic target and was later shown to play a role in the regulation of mitochondrial iron.
The researchers of the current analysis proposed that MitoNEET as a protein can effectively lower mitochondrial iron accumulation in the presence of excessive extra- and intracellular iron and, in this way, provide protection against the production of mitochondrial reactive oxygen species (ROS) and insulin resistance in H9c2 cardiomyoblast cells. Their findings were published in the Journal of Cellular Physiology.
The rare genetic disorder Friedreich ataxia (FA) is characterized by progressively impaired coordination in the extremities and trunk, as well as cardiomyopathy. In addition, approximately one-third of patients with FA develop diabetes. The majority of cases of FA are linked to mutations in the FXN gene, which encodes the protein frataxin. A strong association has been shown between levels of frataxin and mitochondrial iron, with decreased frataxin levels linked to iron overload—that is, an excess of iron—and a tendency toward oxidative stress.
It has been recognized that oxidative stress plays a key role in the pathogenesis of insulin resistance, with some investigators noting that ROS activate stress kinases that may inhibit some components of the insulin signaling pathway. In fact, iron overload had been shown to generate oxidative stress, ROS, and insulin resistance in H9c2 cardiomyoblasts.
Read more about experimental therapies for patients with FA
Because oxidative stress and mitochondrial dysfunction can play major roles in inflammatory diseases, and inflammation has emerged as a significant factor in the pathogenesis of FA, it is thought that the use of MitoNEET in patients with FA may assist in reducing insulin resistance and, in turn, help prevent the development of diabetes in these individuals.
In the current study, H9c2 cells were transfected with the MitoNEET (pMitoN) gene and empty vector plasmids for 48 hours, followed by the selection of clonal cell lines in growth media that contained 500 μg/mL of the G418 antibiotic. Based on Western blot confirmation, the clone H9c2-MitoN, which exhibited the highest expression of MitoNEET, was used for this analysis.
Results of the study offered new insight into the link between mitochondrial iron overload and insulin resistance, with increased mitochondrial iron generating mitochondrial ROS and decreased insulin sensitivity. “This study highlights MitoNEET as a protein that can effectively lower mitochondrial iron accumulation . . . thereby offering protection against mitochondrial ROS production and insulin resistance in [H]9c2 cells,” the researchers concluded.
Reference
Tam E, Sung HK, Sweeney G. MitoNEET prevents iron overload-induced insulin resistance in H9c2 cells through regulation of mitochondrial iron. J Cell Physiol. Published online June 3, 2023. doi:10.1002/jcp.31044
